Methods and instrumentation for the surgical correction of human thoracic and lumbar spinal disease from the lateral aspect of the spine

ABSTRACT

An improved method and instrumentation for performing spinal surgery, including discectomy, interbody fusion and rigid internal fixation of the spine, from the lateral aspect of the spine is disclosed. The surgical procedure can be performed through a very small incision. The instrumentation of the present invention, all of which is inserted from a lateral position into the spine in the preferred embodiment, comprises a guide pin, a distractor, an extended outer sleeve, an inner sleeve an adjustable drill and an implant driver. The distractor of the present invention is driven into the disc for spacing apart and realigning the adjacent vertebrae. It further functions as an alignment rod for inserting the extended outer sleeve which is a hollow tubular member capable of maintaining said spacing and alignment of two adjacent vertebrae and defines a protected space through which subsequent instruments which may include, but are not limited to, a drill and a diameter reducing inner sleeve may be passed, as well as a spinal implant. The remainder of the surgical procedure consisting of the removal of spinal material across the disc, fusion, and rigid internal stabilization via the implant may all be performed via the closed space within the extended outer sleeve.

RELATED APPLICATIONS

[0001] This application is a continuation in part of copending U.S.application Ser. No. 08/074,781 filed on Jun. 10, 1993, which is acontinuation in part of U.S. application Ser. No. 07/698,674 filed onMay 10, 1991 which is a divisional of application Ser. No. 07/205,935filed on Jun. 13, 1988, now U.S. Pat. No. 5,015,247 all of which areincorporated herein by reference. This application is also acontinuation in part of copending U.S. application Ser. No. 08/219,626filed on Mar. 28, 1994 which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to instrumentation andmethods of performing surgical procedures on the human thoracic andlumbar spine along the lateral aspect of the spine and from a truelateral or anterolateral approach, and specifically to the surgicalcorrection of thoracic and lumbar disc disease and spinal deformitieswhere concomitant fusion is desired.

DESCRIPTION OF THE RELATED ART

[0003] As regards the thoracic spine, it may be afflicted with a varietyof ailments, some so severe as to require surgical intervention. A discherniation may compress the spinal cord and/or nerve roots and causepain, loss of function, and even complete paralysis of the legs withloss of bowel and bladder control. The correct treatment for suchconditions is the removal of the offending discal tissue. However, thishas proven both difficult and quite dangerous. When the discs of thethoracic spine are approached posteriorly (from behind) the spinal cordis in the way. To approach the same herniation anteriorly (from thefront) requires the very formidable procedure of thoracotomy (cuttingopen the chest) and moving the heart and lungs out of the way.procedures from a lateral approach to the spine (from the side) usingfiber optic viewing instruments called thorascopes and numerous smallsurgical openings through the chest wall (portals) through which varioussurgical instruments, such as burrs, rongeurs and curettes, may beplaced to remove these disc herniations while avoiding formalthoracotomy. Because the discs are very narrow in the thoracic spine andthe surgeon is approaching the spine laterally, there is very littlespace in which to work as the disc is entered in order to get to theback of the disc space. Therefore, the amount of disc removal may belimited. In the alternative, the surgeon might remove the pedicle togain access to the spinal canal risking further weakening of the alreadydiseased area.

[0004] Sometimes, for a variety of reasons including the removal of discmaterial, the thoracic spine may become unstable (too much motion) atany given level. Historically, this has been treated by fusion, thejoining together permanently of the unstable vertebrae via a bridge ofbone so as to eliminate all motion at that location. Fusions about thethoracic spine have been performed either anteriorly or posteriorly,either procedure being a rather large surgical undertaking.

[0005] Stability of the spine is required for fusion to occur. For thisreason, and for the purpose of correcting spinal deformity, it is oftennecessary to use hardware to rigidly internally fixate (stabilize) thespine. To date, the only benefit the use of the thorascope has providedin this regard is to allow the previous thoracotomy incision to besomewhat smaller.

[0006] So to date the following problems remain even utilizing the mostrecent technology as regards the surgical treatment of thoracic discdisease:

[0007] Firstly, the working space within the disc itself to access theherniation which is more posterior is quite limited.

[0008] Secondly, multiple or long incisions through the chest are stillrequired.

[0009] Thirdly, when fusion is required a major surgical undertakingwith its considerable risks is required.

[0010] Fourthly, the installation of hardware affixed to the spine stillrequires a thoracotomy, albeit a smaller one if visualization isassisted via the thorascope.

[0011] Fifthly, when, as is often the case, the patient requires allthree, that is, discectomy (excision, in part or whole, of anintervertebral disc), fusion, and the application of hardware to thespine, those procedures are performed as serially (one after the other)combined surgical procedures with added surgical times, complications,morbidities, and mortalities.

[0012] As regards to the human lumbar spine, the treatment of discaldisease with neural compression has generally been from a posterior(from behind) approach. This is sensible as the lumbar discs aregenerally quite large and it is only those protrusions occurringposteriorly which compress the neural elements which are themselvesposterior to the discs. These posterior approaches have included bothtrue posterior approaches and posterolateral approaches to the discs.Further, such approaches have been made via open incisions or throughpercutaneous stab wounds. In the latter case, instruments are insertedthrough the stab wounds and monitored by the use of radiographic imagingor the use of an endoscopic viewing device. While it is possible to alsodecompress a posterior disc herniation in the lumbar spine from ananterior approach (from the front) doing so requires the removal of avery substantial portion or all of the disc material in the front andmid portions of the disc thus leaving that disc incompetent and thatspinal segment generally unstable. Therefore, such an anterior approachto the lumbar spine has been reserved for those instances where a fusionis to be performed in conjunction with, and following such a discremoval.

[0013] As regards to fusion, the application of bone or bone likesubstances between bones to induce bony bridging, such procedures havebeen performed outside the vertebral bodies and/or between the vertebralbodies. The latter being known as an interbody fusion. Such interbodyfusions have been performed from posterior, posterolateral and anterior.The adjective applying specifically to the direction from which the bonegrafts enter the intervertebral space. Interbody fusion from theposterior approach while still in use has been associated withsignificant complications generally related to the fact that thedelicate dural sac and the spine nerves cover the back of the disc spaceand are thus clearly in harms way with such an approach. Theposterolateral approach has generally been utilized as a compliment topercutaneous discectomy and has consisted of pushing tiny fragments ofmorsalized bone down through a tube and into the disc space.

[0014] Anterior interbody spinal fusion is performed from a straightanterior position as regards the path of entry of the fusion materialinto the intervertebral space. Such an anterior position is achieved inone of two ways. First, by a straight anterior approach which requiresthat the peritoneal cavity, which contains the intestines and otherorgans, be punctured twice, once through the front and once through theback on the way to the front of the spine; or secondly, by starting onthe front of the abdomen off to one side and dissecting behind theperitoneal cavity on the way to the front of the spine. Regardless ofwhich approach to the front of the spine is used, and apart from theobvious dangers related to the dense anatomy and vital structures inthat area, there are at least two major problems specific to theanterior interbody fusion angle of implant insertion itself. First,generally at the L₄L₅ disc, the great iliac vessels bifurcate from theinferior vena cava lie in close apposition to, and, covering that discspace making fusion from the front both difficult and dangerous.Secondly, anterior fusions have generally been done by filling the discspace with bone or by drilling across the disc space and then fillingthose holes with cylindrical implants. As presently practiced, thepreferred method of filling the disc space consists of placing a ring ofallograft (bone not from the patient) femur into that disc space. Anattempt to get good fill of the disc space places the sympathetic nervesalong the sides of the disc at great risk. Alternatively, when the doweltechnique is used, because of the short path from the front of thevertebrae to the back and because of the height of the disc as comparedto the width of the spine, only a portion of the cylindrical implant orimplants actually engages the vertebrae, thus, compromising the supportprovided to the vertebrae and the area of contact provided for thefusion to occur.

[0015] There is therefore, in regard to the lumbar spine, a need for anew method and means for achieving interbody fusion which method avoidsthe problems associated with all prior methods, and which have included,but are not limited to, nerve damage when performed posteriorly, or theneed to mobilize the great vessels when performed anteriorly. Further,the size of the implants are limited by the dural sac posteriorly, andthe width of the spine and the delicate vital structures therewithassociated anteriorly. An improved method and means for interbody fusionshould provide for optimal fill of the interspace without endangeringthe associated structures and allow for the optimal area of contactbetween the implant or implants and the vertebrae to be fused.

SUMMARY OF THE INVENTION

[0016] The present invention is directed to methods and instrumentationfor performing surgery on the spine along its lateral aspect (side) andgenerally by a lateral or an anterolateral surgical approach, such thatthe instruments enter the body from an approach that is other thanposterior and make contact with the spine along its lateral aspect. Thepresent invention provides for the entire surgical procedure to beperformed through a relatively small incision and may be performed ineither the thoracic or lumbar spine.

[0017] In the preferred embodiment, the instrumentation of the presentinvention comprises a guide pin, a distractor, an extended outer sleeve,an inner sleeve and drill adjustable for depth and with a depth limitingmeans. The distractor of the present invention is used for initiallydistracting (spacing apart) and realigning adjacent vertebrae of thespine and also functions as an alignment rod for inserting the extendedouter sleeve. The distractor is placed at the affected disc spacebetween adjacent vertebrae through a small incision in the body. Forexample, for surgery in the thoracic spine, a small incision in thechest cavity of the patient is made from a lateral approach to thethoracic spine. For surgery in the lumbar spine a small incision may bemade in the abdominal wall of the patient. The insertion of thedistractor may be guided by a guide pin previously inserted in the discspace and visually monitored for proper orientation and placement by thesurgeon either indirectly through an image intensifier, or directlythrough a thorascope or by direct vision.

[0018] The extended outer sleeve in the preferred embodiment is a hollowtubular member having an extension member that is inserted in the discspace and is capable of distracting and aligning the two adjacentvertebrae from the lateral aspect of the spine. In the preferredembodiment, the extended outer sleeve has a pair of prongs for fixedlyengaging the two adjacent vertebrae and further stabilizing the adjacentvertebrae. With the distractor in place in the affected disc space, theextended outer sleeve is placed over the distractor, and the distractorguides and aligns the insertion of the extended outer sleeve. As theextended outer sleeve is seated, the extension member becomes insertedin the disc space and the prongs engage the outside wall of the adjacentvertebrae. The distractor is then removed and the extended outer sleevemaintains the proper distraction and alignment of the adjacentvertebrae. The remainder of the surgical procedure consisting of discremoval, fusion, and rigid internal stabilization may all be performedvia the closed space within the extended outer sleeve. Alternatively, aconvertible extended outer sleeve comprising a hollow tubular memberthat can be dissociated from its insertion end which remains engaged tothe vertebrae to maintain distraction and alignment, may be used whereit is desired to have direct visualization and access to the surgicalsite for at least a portion of the surgical procedure.

[0019] The drilling out and the subsequent removal of a rathersignificant mass of the disc itself may be curative in relieving aposterior disc herniation as the mass of tissue pushing from within thedisc outward and posteriorly is thus removed. Further, the distractor indriving the vertebrae apart exerts significant tension on the walls ofthe disc which are pulled straight also tending to correct any discherniation. Finally, since the hole drilled across the disc space isquite close to the posterior borders of the vertebrae, it makes theremoval of any persisting posterior disc herniation quite simple. Withthe drill removed and the extended outer sleeve cleaned out byirrigation and suction, one can then place the endoscope directly downthe outer sleeve and into the large space created by the removal of thedisc, and in the preferred method, the adjacent vertebral bone, and thenremove any remaining fragments of disc using conventional hand heldinstruments such as rongeurs and curettes under endoscopicvisualization.

[0020] When it is desirable to remove posterior disc material, then aspecialized modification of the extended outer sleeve having at itsdistal end a spine engaging portion comprising one anterior extensionand posteriorly two prongs one each above and below the disc space maybe used. Further, such an extended outer sleeve may be configured suchthat the great length of the hollow tubular portion of the extendedouter sleeve is detachable, as by unscrewing, from the distal workingend such that when uncoupled the distal end may remain in placemaintaining distraction even after the hole is drilled and thus allowingthe surgeon to work through that remaining portion of the extended outersleeve and the space provided by the drilling to remove the posteriordisc material under direct vision. For those instances where the surgeonhas elected to access the spine through a more standard incision and isviewing the spine directly, the surgeon is then able to continue tooperate through the distal spine engaging portion of the extended outersleeve and still maintain the distraction and alignment of thevertebrae.

[0021] A spinal implant may then be inserted through the extended outersleeve and into the hole in the adjacent vertebrae. The extended outersleeve is removed once the spinal implant has been inserted. If thespinal implant being inserted has surface projections such as a thread,then an inner sleeve is inserted in the extended outer sleeve prior todrilling to accommodate the height of the projections or as in the caseof a thread, the difference between the major and minor diameters of theimplant.

[0022] To further stabilize the spinal implant, a staple alignment rodmay be mechanically coupled to the spinal implant prior to the removalof the extended outer sleeve. The extended outer sleeve is then removedand a staple having spine engaging prongs is inserted via the alignmentrod and is coupled to the spinal implant. The alignment rod is removedand replaced with a locking screw to secure the staple to the spinalimplant.

[0023] While the preferred method utilizing a cylindrical implant andinvolving the removal of some bone from each of the adjacent vertebraein preparation for fusion has been described, it is understood that thedistractor and sleeve could as well be rectangular and the drillsupplemented with or replaced by a box chisel, or other chisel so as toproduce a rectangular fusion site or similarly any of a variety ofshapes. Further, it is understood that the outer sleeve could bedimensioned so as to confine the removal of the disc material,regardless of the means, to the area between the adjacent vertebraerather than providing for the removal of the bone as well.

OBJECTS OF THE PRESENT INVENTION

[0024] It is an object of the present invention to provideinstrumentation for performing surgery on the thoracic spine through thechest cavity from a lateral approach to the spine.

[0025] It is another object of the present invention to provide a methodof performing surgery on the thoracic spine through the chest cavityfrom a lateral approach to the spine that is safer, more effective andfaster than previously possible.

[0026] It is a further object of the present invention to provideinstrumentation and method of inserting a spinal implant in a holedrilled across the disc space and into two adjacent vertebrae of thethoracic spine through the chest cavity from a lateral approach to thespine.

[0027] It is another object of the present invention to provide for amethod and instrumentation for performing a thoracic discectomy, aninterbody fusion, and rigid internal fixation of the spine through thechest cavity from a lateral approach and all as a single integratedprocedure.

[0028] It is yet another object of the present invention to provide fora method and instrumentation for performing a lumbar fusion from thelateral aspect of the spine.

[0029] It is further another object of the present invention to providefor a method and instrumentation for performing a lumbar fusion andspinal canal decompression from the lateral aspect of the spine.

[0030] It is further still another object of the present invention toprovide for a method and instrumentation for performing a lumbar fusion,decompressive discectomy, and a rigid internal fixation of the spine andall as a single integrated surgical procedure.

[0031] It is further yet another object of the present invention toprovide for a method and instrumentation to achieve discectomy, fusionand interbody stabilization of the lumbar without the need to mobilizethe great vessels from the front of the vertebral bodies.

[0032] These and other objects of the present invention will becomeapparent from a review of the accompanying drawings and the detaileddescription of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a rear perspective view of a segment of the thoracicspine with the guide pin of the present invention about to be insertedfrom a lateral approach to the thoracic spine into the disc spacebetween two adjacent vertebrae.

[0034]FIG. 2 is a rear perspective view of a segment of the thoracicspine with the guide pin inserted in the disc space between two adjacentvertebrae and the distractor of the present invention about to be placedover the guide pin.

[0035]FIG. 3 is an enlarged front elevational view of a segment of thethoracic spine along line 3 of FIG. 2 having a portion of the topvertebrae removed and a portion of the disc removed with the guide pin,shown partially in hidden line, inserted from a lateral approach to thethoracic spine into the disc space.

[0036]FIG. 4 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the guide pin and distractor, shownpartially in hidden line, inserted from a lateral approach to thethoracic spine in the disc space.

[0037]FIG. 5 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the distractor, shown partially in hiddenline, inserted from a lateral approach to the thoracic spine and seatedin the disc space and the guide pin removed.

[0038]FIG. 6 is a rear perspective view of a segment of the thoracicspine having a distractor inserted from a lateral approach to thethoracic spine and seated in the disc space and the extended outersleeve of the present invention coupled to a driver cap and about to beplaced over the distractor.

[0039]FIG. 7 is an enlarged front elevational view of the segment of thethoracic spine of FIG. 3 with the distractor and the extended outersleeve inserted from a lateral approach to the thoracic spine and seatedin the disc space.

[0040]FIG. 7A is side perspective view of the extended outer sleeve ofthe present invention.

[0041]FIG. 8 is a rear perspective view of a portion of the thoracicspine with the extended outer sleeve fully seated over the distractorinserted from a lateral approach to the thoracic spine and seated in thedisc space and with the driver cap removed.

[0042]FIG. 9 is a front elevational view of a segment of the thoracicspine of FIG. 3 with the extended outer sleeve inserted from a lateralapproach to the thoracic spine and seated in the disc space and engagingthe adjacent vertebrae showing the distractor being removed by adistractor puller.

[0043]FIG. 10 is an enlarged front elevational view of the segment ofthe thoracic spine of FIG. 3 with the extended outer sleeve insertedfrom a lateral approach to the thoracic spine and seated in the discspace and engaging the two adjacent vertebrae.

[0044]FIG. 11 is a front elevational view of a segment of the thoracicspine of FIG. 3 with the inner sleeve of the present invention beinginserted into the extended outer sleeve.

[0045]FIG. 12 is an enlarged front elevational view of the segment ofthe thoracic spine of FIG. 3 with the inner sleeve, shown in partialhidden line, inserted into the extended outer sleeve that is insertedfrom a lateral approach to the thoracic spine in the disc space andengages two adjacent vertebrae.

[0046]FIG. 13 is a side elevational view of a segment of the thoracicspine of FIG. 3 showing the extended outer sleeve inserted from alateral approach to the thoracic spine in the disc space and engagingthe two adjacent vertebrae with the inner sleeve and drill shown in anexploded view and partially in hidden line.

[0047]FIG. 14 is a cross sectional view along lines 14-14 of FIG. 13 ofthe drill, inner sleeve and extended outer sleeve.

[0048]FIG. 15 is a cross sectional view along lines 15-15 of FIG. 13 ofthe collar for limiting the drilling depth of the drill.

[0049]FIG. 16 is an enlarged front elevational view of the segment ofthe thoracic spine of FIG. 3 showing the extended outer sleeve insertedfrom a lateral approach to the thoracic spine and seated in the discspace and engaging the two adjacent vertebrae, the inner sleeve insertedin the extended outer sleeve, and the drill passing through the innersleeve to create a hole across the disc space and into the adjacentvertebrae.

[0050]FIG. 17 is an enlarged front elevational view of the segment ofthe thoracic spine of FIG. 3 with the extended outer sleeve insertedfrom a lateral approach to the thoracic spine and seated in the discspace and engaging the two adjacent vertebrae illustrating a holedrilled across the disc space and into the adjacent vertebrae.

[0051]FIG. 18 is a front elevational view of the segment of the thoracicspine of FIG. 3 showing the extended outer sleeve inserted from alateral approach to the thoracic spine and seated in the disc space andengaging the two adjacent vertebrae, an implant driver, and a spinalimplant about to be inserted through the extended outer sleeve and intothe hole drilled across the disc space and into the adjacent vertebrae.

[0052]FIG. 19 is a front elevational view of the segment of the thoracicspine of FIG. 3 showing the extended outer sleeve inserted from alateral approach to the thoracic spine and seated in the disc space andengaging the two adjacent vertebrae and a spinal implant implanted inthe hole drilled across the disc space and into two adjacent vertebrae.

[0053]FIG. 20 is a front elevational view of the segment of the thoracicspine of FIG. 3 showing the extended outer sleeve inserted from alateral approach to the thoracic spine and seated in the disc space andengaging the two adjacent vertebrae and an extractor cap for removingthe extended outer sleeve about to be coupled to the extended outersleeve.

[0054]FIG. 21 is an enlarged partial sectional view of the extractor capengaging the extended outer sleeve.

[0055]FIG. 22 is a front elevational view of the segment of the thoracicspine of FIG. 20 with the distractor puller coupled to the extractor capshown removing the outer sleeve from the disc space and the adjacentvertebrae in the direction of the arrow.

[0056]FIG. 23 is an enlarged front elevational view of a segment of thethoracic spine having a portion of the top vertebrae removed and aportion of the disc space removed and a spinal implant implanted from alateral approach to the thoracic spine in the hole drilled across thedisc space and into the two adjacent vertebrae.

[0057]FIG. 24 is a front elevational view of a segment of the thoracicspine having a spinal implant implanted from a lateral approach to thethoracic spine into a hole drilled across the disc space and into theadjacent vertebrae with a spinal fixation device coupled to the spinalfusion implant and engaging the adjacent vertebrae to lock the spinalimplant in place.

[0058]FIG. 25 is a side perspective view of an alternative embodiment ofthe extended outer sleeve of the present invention having a pair ofextension members and a pair of prongs.

[0059]FIG. 26 is a top plan view of the extended outer sleeve of FIG. 25shown in partial cutaway with an inner sleeve and a drill insertedwithin its interior and placed adjacent to a vertebra of the spine withthe major vessels and the dural sac and spinal nerves proximate to thevertebra shown in cross section.

[0060]FIG. 27 is an anterior elevational view of a vertebra of the spinewith the extended outer sleeve of FIG. 25 shown inserted from thelateral approach and seated in the disc space and engaging the vertebra.

[0061]FIG. 28 is a posterior elevational view of a vertebra of the spinewith the extended outer sleeve of FIG. 25 shown inserted from thelateral approach of the spine and seated in the disc space and engagingthe vertebra.

[0062]FIG. 29 is a side elevational view of a segment of the lumbarspine with a first spinal implant inserted from the lateral aspect intoa hole drilled across a first disc space and into two adjacentvertebrae, and a second spinal implant inserted from the lateral aspectinto a second hole drilled across a second disc space and into twoadjacent vertebrae.

[0063]FIG. 30 is top sectional view along lines 30-30 of FIG. 29 showingthe area of contact of the first spinal implant and the vertebra.

[0064]FIG. 30A is a top sectional view similar to FIG. 30 showing thearea of contact of a spinal implant inserted from slightly anterior(anterolateral) along the lateral aspect of the spine and oriented atleast partially from side to side with respect to the vertebra.

[0065]FIG. 31 is an anterior elevational view of a segment of the lumbarspine with spinal cylindrical implants inserted from the anterior of thespine into holes drilled across the same disc space and into twoadjacent vertebrae.

[0066]FIG. 32 is a top sectional view along lines 31-31 of FIG. 31showing the area of contact of the two spinal implants and the vertebrawhich is the same size as the vertebra of FIG. 30.

[0067]FIG. 33 is a top sectional view of a single implant having adiameter equal to the diameter of the implant of FIG. 30 showing thearea of contact with the vertebra which is the same size as the vertebraof FIG. 30.

[0068]FIG. 34 is a side elevational view of a segment of the spinalcolumn with two spinal implants inserted from front to back at adjacentdisc levels between three vertebrae.

[0069]FIG. 35 is a perspective side view of an alternative embodiment ofthe extended outer sleeve of the present invention having a removabledistal end with a single extension member and a pair of prongs.

DETAILED DESCRIPTION OF THE DRAWINGS

[0070] Referring to FIG. 1, a rear perspective view of a segment of thethoracic spine S is shown with a guide pin 30 about to be inserted froma lateral approach (through the lateral chest wall) to the thoracicspine S into the disc space D between two adjacent vertebrae, forexample vertebrae T₇ and T₈. The guide pin 30 may first be used asradiological marker to confirm the correct disk level and instrumentposition, and then functions to align and guide the insertion of theinstrumentation described below into the disc space D. The guide pin 30is inserted through a small incision on the side of a patient's chestcavity perpendicular to the lateral aspect of the vertebrae T₇ and T₈ ofthe thoracic spine S. The guide pin 30 is made of a material appropriatefor surgical use and comprises a shaft portion 40, a tip 50 which may bepointed to facilitate insertion into the disc space D, and a distal end60. In the preferred embodiment, the guide pin has a diameter in therange of 1.5 mm to 5.0 mm, with 2.5 mm being the preferred diameter, anda length in the range of 200 mm to 800 mm, with 350 mm being thepreferred length.

[0071] Referring to FIGS. 2 and 3, the guide pin 30 is shown insertedfrom a lateral approach to the thoracic spine S and into the disc spaceD between adjacent vertebrae T₇ and T₈, with a substantial part of theshaft portion 40 of the guide pin 30 remaining external to the discspace D and functions as a guide post. The tip 50 of the guide pin 30may penetrate the disc space D for a substantial part of the transversewidth W of the vertebrae T₇ and T₈ such that at least a part of theshaft portion 40 is within the disc space D. The guide pin 30 is firmlyembedded in the discal material present within the disc space D, butdoes not protrude through the opposite side of the disc space D toprevent any unwanted damage to that area. The guide pin 30 is placed inthe disc space D so that it is parallel to the end plates of thevertebrae T₇ and T₈, and centered within the disc space D to bisect thedisc space D along the transverse width W of the vertebrae T₇ and T₈. Inthis manner, a substantial portion of the vertebrae T₇ and T₈ is presentnear the circumference of the guide pin 30 such that instruments havinga diameter greater than the guide pin 30 may be inserted into thevertebrae T₇ and T₈ coaxial to the guide pin 30 without protruding fromthe vertebrae T₇ and T₈. Such instruments are guided and aligned duringinsertion by the guide pin 30 so that they are correctly oriented withrespect to the vertebrae T₈ and T₈. The surgeon may monitor the correctorientation of the guide pin 30 within the disc space D indirectly withan image intensifier, or directly with a thorascope if one is beingused.

[0072] Once inserted in the disc space D, the guide pin 30 functions asa guide post for a distractor 100 which is placed over the guide pin 30and inserted in the disc space D to distract the disc space D and alignthe adjacent vertebrae T₇ and T₈ by urging them apart. Circumstancespermitting, the surgeon may elect to bypass the use of the guide pin 30and insert the distractor 100 directly. The distractor 100 has acylindrical barrel 106 that terminates at one end in a reduced diameterdisc penetrating portion 102 that is essentially cylindrical, with afurther reduced diameter, bullet-shaped front end 103 to facilitateinsertion into the disc space D. The distractor 100 has a shoulderportion 104 where the penetrating portion 102 extends from barrel 106and has a hollow longitudinal passageway 107 extending the entire lengthof the distractor 100 for receiving the guide pin 30. The passageway 107of the distractor 100 is open at both ends of the distractor 100 and hasa diameter that is slightly greater than the diameter of the shaftportion 40 of guide pin 30. The shaft portion 40 of the guide pin 30 maypass through the passageway 107 as the distractor 100 is placedcoaxially over the guide pin 30. In this manner, the distractor 100 canbe guided and aligned by the guide pin 30 so that it is inserted intothe disc space D coaxial to the guide pin 30 and is properly alignedwith respect to the vertebrae T₇ and T₈. Once the distractor 100 isproperly placed within the disc space D, the guide pin 30 may be removedfrom the disc space D through the passageway 107 of the distractor 100.

[0073] The appropriate placement of distractor 100 in the disc space Dmay be determined visually by the surgeon by the use of a thorascope andor by the use of radiographic, fluoroscopic, or similar procedures; suchas utilizing an image intensifier, all of which allow the surgeon todetermine the correct orientation and placement of the guide pin 30 anddistractor 100 within the disc space D. The correct orientation andplacement of the distractor 100 is important to the success of themethod of the present invention, as the purpose of the distractor 100 isto space part and align the vertebrae T₇ and T₈ and to guide theinsertion into the disc space D of the extended outer sleeve 140described in detail below. As the diameter of the distractor 100 isalmost the same as the inner diameter of the extended outer sleeve 140and is the same as the spinal implant I, also described in detail below,the surgeon can use x-rays to determine whether the distractor 100 isproperly oriented with respect to the adjacent vertebrae T₇ and T₈, suchthat any subsequent drilling through the extended outer sleeve 140 andinsertion of spinal implant I will be correctly oriented with respect tothe vertebrae T₇ and T₈. Such a precaution will permit the surgeon tocorrect any misplacement of the distractor 100 before any irreversibledrilling or implant insertion has occurred.

[0074] The penetrating portion 102 of the distractor 100 may be ofvarious diameters and lengths, the preferred length being less than theknown transverse width W (side to side) of the vertebrae T₇ and T₈. Thiscombined with the circumferential shoulder portion 104 of the distractor100, which is too large to fit within the disc space D, protects againstthe danger of over penetration. The barrel 106 of the distractor 100 mayhave at its distal end a recessed portion 108 below the crown 110 whichallows for the distractor 100 to be engaged by an extractor unit shownin FIG. 9.

[0075] In the preferred embodiment of the distractor 100, the barrel 106has a diameter in the range of 10 mm to 30 mm, with 20 mm being thepreferred diameter, and the penetrating portion 102 has a diameter inthe range of 3 mm to 10 mm, with 6 mm being the preferred diameter.

[0076] Referring to FIGS. 4 and 5, once the distractor 100 is insertedinto the disc space D, the penetrating portion 102 of the distractor 100distracts the vertebrae T₇ and T₈ apart, such that the vertebrae T₇ andT₈ to either side of the penetrating portion 102 are forced into fullcongruence and thus become parallel, not only to the penetrating portion102, but to each other. Because of the forced opposition of thevertebrae T₇ and T₈ to the penetrating portion 102 the distractor 100will then come to lie absolutely perpendicular to the plane P of thelateral aspect of the thoracic spine S and absolutely parallel to thevertebral endplates, allowing optimal alignment for the procedure to beperformed.

[0077] Referring to FIGS. 6, 7 and 7A, the distractor 100 now serves asboth a centering post and an alignment rod for the extended outer sleeve140 which is fitted over the distractor 100 and inserted into the discspace D. As shown in FIG. 7A, the extended outer sleeve 140 is a hollowtubular member made of material appropriate for surgical use andpreferably metal, and has an inner diameter sufficiently sized toreceive the distractor 100. The inner diameter of the extended outersleeve 140 closely matches the outer diameter of the distractor 100, sothat a close fit is achieved and the extended outer sleeve 140 isprecisely guided by the distractor 100. The extended outer sleeve 140has at its distal end 146 an extension member 148 and two prongs 149 and150 sufficiently spaced apart to penetrate and hold fixed the twoadjacent vertebrae T₇ and T₈. The extension member 148 is essentially acontinuation of the extended outer sleeve 140 and the prongs 149 and 150are offset from the extended outer sleeve 140 or can also be acontinuation of the extended outer sleeve 140 like extension member 148.The prongs 149 and 150 may have sharp insertion edges 152 and 154 tofacilitate insertion into the vertebrae T₇ and T₈.

[0078] Where the surgery is for a disc herniation, the extension member148 of the extended outer sleeve 140 located anteriorly is used withouta second extension member posteriorly, as the use of the two prongs 149and 150 in conjunction with the anterior extension member 148 makes itpossible to operate through the extended outer sleeve 140 posteriorly,without obstruction and with good visibility when an endoscope is usedsuch that any remaining disc herniation may be removed. The extensionmember 148 of the extended outer sleeve 140 provides a protectivebarrier to the structures lying beyond it.

[0079] However, if the surgery is not for a disc herniation, but forexample, for stabilization of the spine, then the extended outer sleevemay have both an anterior extension member 148 and a correspondingposterior extension member with or without prongs, such as the extendedouter sleeve 1100 shown in FIG. 35 and described in greater detailbelow.

[0080] In the preferred embodiment, the extension member 148 of theextended outer sleeve 140 functions to maintain the distraction andalignment of the vertebrae T₇ and T₈, as the extension member 148 isbeing inserted from the lateral aspect of the thoracic spine S. Withoutthe extension member 148, in order to maintain the proper distraction ofthe adjacent vertebrae T₇ and T₈, it would be necessary to place asurgical instrument, such as a second distractor (not shown) on theopposite side of the vertebrae T₇ and T₈. This would require a secondincision in the opposite side of the patient's chest cavity forinsertion of the required surgical instruments. Further, as it isdesired to insert an implant of the maximum possible length across thetransverse width W of the vertebrae T₇ and T₈, the presence of anyinstrumentation at the opposite end of the vertebrae T₇ and T₈, wouldinterfere with the insertion of such an implant. For example, the seconddistractor on the opposite side of the vertebrae T₇ and T₈ would be inthe way of a drill used to create a hole across the transverse width Wof the vertebrae T₇ and T₈, since the drilled opening would overlap thesecond distractor. Therefore, the extension member 148 solves theproblem of maintaining an even distraction of the two adjacent vertebraeT₇ and T₈ across their transverse width W from only one side of thethoracic spine S, allowing for the unimpeded insertion of instrumentsand/or implants. While in the preferred embodiment, the extended outersleeve 140 has an extension member 148, it is also possible to have anextended outer sleeve without any extension members and instead, havingprongs of sufficient length that engage the bone of the adjacentvertebrae to maintain the distraction and alignment of the adjacentvertebrae created by the distractor 100. However, the use of such anextended outer sleeve capable of holding, but not of obtaining, thedesired intervertebral distraction and alignment would require the useof a distractor prior to its insertion as earlier described herein.

[0081] In the preferred embodiment of the extended outer sleeve 140, asingle extension member 148 is present and oriented anteriorly toprotect the major vessels located to the anterior aspect of the thoracicspine S. The extended outer sleeve 140 has no extension member near theposterior aspect the spine as it is often necessary to access the spinalcanal in order to remove any diseased discal material. In the specialcircumstances where only vertebral fusion is desired, the extended outersleeve 140 may have a second extension member (not shown) identical tothe extension member 148 positioned diametrically opposite the extensionmember 148 in order to protect the spinal canal, and in such instancemay or may not have the bone penetrating prongs 149 and 150.

[0082] The extension member 148 of the extended outer sleeve 140 has aheight that is generally approximately equal to the diameter of thepenetrating portion 102 of the distractor 100, such that the extensionmember 148 is capable of maintaining the spacing created by theinsertion of the distractor 100 between the adjacent vertebrae T₇ and T₈which is generally the restoration to normal of the disc space D. Theextension member 148 is tapered at its leading edge 151 to facilitateinsertion into the disc space D and is positioned approximately 120degrees from each of the two prongs 149 and 150. The extension member148 of the extended outer sleeve 140 works in conjunction with theprongs 149 and 150 which engage the vertebrae T₇ and T₈, respectively,to maintain the distraction and alignment of the vertebrae T₇ and T₈.Further, the prongs 149 and 150 not only hold the vertebrae T₇ and T₈apart, but during drilling also help to hold them together so as toresist them moving apart.

[0083] In the preferred embodiment, the extension member 148 of theextended outer sleeve 140 has a length that is less than the transversewidth w of the vertebrae T₇ and T₈. The extension member 148 needs to berelatively long because it must maintain distraction of the adjacentvertebrae T₇ and T₈ when placed across the transverse width W of thevertebrae T₇ and T₈. Therefore, if the extension member 148 is shorterthan one half the transverse width W of the vertebrae T₇ and T₈, it maynot be capable of distracting and aligning the vertebrae T₇ and T₈, anda second distractor would be required as described above, to achieve thecorrect distraction and alignment of the vertebrae T₇ and T₈.

[0084] In the preferred embodiment, the extended outer sleeve 140 has anouter diameter in the range of 12 mm to 34 mm, with 24 mm being thepreferred outer diameter, and an inner diameter in the range of 10 mm to28 mm, with 20 mm being the preferred inner diameter of the extendedsleeve 140.

[0085] In the preferred embodiment, the extension member 148 of theextended outer sleeve 140 has a length in the range of 14 mm to 30 mm,with 24 mm being the preferred length, and a height in the range of 3 mmto 10 mm, with 6 mm being the preferred height. In the preferredembodiment, the prongs 149 and 150 of the extension member 140 have alength in the range of 6 mm to 20 mm, with 14 mm being the preferredlength and a diameter in the range of 2 mm to 3 mm, with 2 mm being thepreferred diameter of the prongs 149 and 150.

[0086] Referring specifically to FIG. 6, coupled to the proximal end 157of the extended outer sleeve 140 is a driver cap 160 in the form of animpaction cap which has at its far end a flat, closed-back surface 162and at its other end a broad, circular opening. The driver cap 160 isused for driving the extended outer sleeve 140 toward the vertebrae T₇and T₈ and fits over both the extended outer sleeve 140 and thedistractor 100. An impaction force, such as a mallet blow, is applied tosurface 162 of the driver cap 160 to advance the extended outer sleeve140. That force is transmitted to the extended outer sleeve 140 via itsproximal end 157, seating the prongs 149 and 150 of the extended outersleeve 140 into the vertebrae T₇ and T₈ and inserting the extensionmember 148 into the disc space D. As the extended outer sleeve 140 isadvanced forward, the crown 110 of the distractor 100 is allowed toprotrude within the driver cap 160 unobstructed until it contacts theinterior of the driver cap 160, such that further taps of the malletwill not further advance the extended outer sleeve 140. Any furthermotion is resisted by the flat shoulder portion 104 of the distractor100 abutting the hard lateral outer surfaces of the adjacent vertebraeT₇ and T₈. The flat, planar area 156 of the distal end 146 of extendedouter sleeve 140 serves to resist the further insertion of the extensionmember 148 into the disc space D and to resist further insertion of theprongs 149 and 150 into the vertebrae T₇ and T₈. In this way, theextended outer sleeve 140 is safely and assuredly inserted to itsoptimal depth, and no further, and rigidly secures the two adjacentvertebrae T₇ and T₈ as shown in FIG. 7.

[0087] Referring to FIGS. 8 and 9, the driver cap 160 is then removedand the crown 110 and the recessed portion 108 of the distractor 100protrude from the proximal end 157 of the extended outer sleeve 140. Thedistractor 100 may now be removed from within the extended outer sleeve140 since the extended outer sleeve 140 functions to maintain thedistraction and alignment of the vertebrae T₇ and T₈. The extended outersleeve 140 is held secure by the extension member 148 inserted withinthe disc space D and by the prongs 149 and 150 engaging the vertebrae T₇and T₈.

[0088] A distractor puller 200 is utilized to remove the distractor 100in the direction of arrow Y from within the disc space D leaving theextended outer sleeve 140 in place. The distractor puller 200 has frontportion 202, a mid portion 204, and a back handle portion 206. The frontportion 202 of the distractor puller 200, is connected to one end ofshaft 210 which at its far end is connected to the back handle portion206. The distractor puller 200 is described in detail in copendingapplication Ser. No. 08/074,781, entitled APPARATUS AND METHOD FORINSERTING SPINAL IMPLANT, and is incorporated herein by reference. Thesocket-like front portion 202 of the distractor puller 200 engages thecircumferential recessed portion 108 of the distractor 100.

[0089] A cylindrical and freely movable weight 216 is fitted aroundshaft 210 between the front portion 202 and the rear handle portion 206of the distractor puller 200 so as to form a slap hammer. The weight 216of the distractor puller 200 is gently and repeatedly slid along theshaft 210 and driven rearwardly against flat surface 228 of the rearhandle portion 206 to transmit a rearward vector force to front portion202 and to the distractor 100 to which it is engaged. In this manner,the distractor 100 is removed from within the disc space D and out ofthe extended outer sleeve 140 without disturbing it.

[0090] Referring to FIG. 10, once the distractor 100 has been completelyremoved from within the extended outer sleeve 140 and from within thedisc space D, the extension member 148 remains within the disc space Dand the prongs 149 and 150 rigidly maintain the appropriate distractionand the relative position of the adjacent vertebrae T₇ and T₈. Theremainder of the procedure occurs entirely through the extended outersleeve 140 and the space therein is sealed off from any of the organs ofthe chest.

[0091] Referring to FIGS. 11 and 12, since the extended outer sleeve 140is of a fixed length and rigid, the flat rearward surface 172 of thedistal end 146 may be used as a stop to the advancement of anyinstruments placed through the extended outer sleeve 140, thusprotecting against accidental over penetration. Further, the extendedouter sleeve 140 assures that the further procedure to be performed willoccur coaxial to the disc space D and further, be symmetrical in regardto each of the adjacent vertebrae T₇ and T₈.

[0092] Where it is desirable to drill a hole smaller in diameter thanthe spinal implant to be inserted, such as in the case where the spinalimplant is threaded, an inner sleeve 242 which functions as a drillguide and spacer having a thickness which corresponds to the differencebetween the major and minor diameters of the spinal implant, is insertedin the proximal end 158 of the extended outer sleeve 140. The innersleeve 242 is a hollow tubular member comprising a barrel portion 243and a cuff portion 244 having a greater outer diameter than the barrelportion 243. The cuff portion 244 of the inner sleeve 242 seats againstthe flat rearward surface 172 of the extended outer sleeve 140 toprevent further insertion of the inner sleeve 242. The distal end 246 ofthe inner sleeve 242 extends towards but does not impact the lateralaspect of the adjacent vertebrae T₇ and T₈ in the interior of theextended outer sleeve 140 when fully seated. The barrel portion 243 ofthe inner sleeve 242 has an outer diameter that fits within the innerdiameter of the extended outer sleeve 140. In the preferred embodiment,the barrel portion 243 of the inner sleeve 242 has an outside diameterin the range of 10 mm to 28 mm, with 20 mm being the preferred outerdiameter, and a wall thickness in the range of 0.5 mm to 3 mm, withapproximately 0.75 to 1.5 mm being the preferred thickness.

[0093] Referring to FIGS. 13-15, once the inner sleeve 242 is seatedwithin the extended outer sleeve 140, a drill 250 connected to a handle260 or to a drill motor (not shown), is introduced through the aperturein the proximal end 248 of the inner sleeve 242 and utilized to create ahole across the disc space D and into the adjacent vertebrae T₇ and T₈.The drill 250 reams out arcs of bone which it engages from the adjacentvertebrae T₇ and T₈, as well as any discal material within its path downto its predetermined and limited depth. It is appreciated that if aninner sleeve 242 is not used, the drill 250 may be placed directly intothe extended outer sleeve 140 to create a hole across the disc space Dand into the adjacent vertebrae T₇ and T₈.

[0094] The drill shaft of drill 250 comprises an upper portion 252, acentral recessed portion 254 of a smaller diameter and a lower cuttingportion 256. The drill 250 has a narrow engagement portion 258, whichallows it to be affixed to a driving mechanism which may be either amanual unit such as, handle 260, or a power unit such as an electricdrill motor. The upper portion 252 has a plurality of grooves 261 forengaging a circumferential collar 262 of an increased diameter whichserves to limit the depth of penetration of the drill 250 and may befixed, or lockably adjustable.

[0095] Referring to FIG. 15, a cross sectional view of thecircumferential collar 262 is shown engaging the upper portion 252 ofthe shaft of drill 250. The collar 262 comprises diametrically oppositefirst and second flanges 264 and 266. The first and second flanges 264and 266 are pivotably attached to the collar 262 by first and secondpins 268 and 270 and spring biased by first and second spring 272 and274. The first and second flanges 264 and 266 of the collar 262 arecontoured to correspond to the curvature of the upper portion 252 of thedrill 250. The first and second flanges 264 and 266 engage one of thegrooves 261 when in the full biased position as shown in FIG. 15. Todisengage the grooves 261, the first and second 264 and 266 arecompressed together by the surgeon such that the first and secondsprings 272 and 274 are compressed and the first and second flanges 264and 266 pivot away from the upper portion 252 of the shaft, such thatthe collar 262 can slide along the upper portion 252 of the drill 250.The first and second flanges 264 and 266 of the collar 262 are orientedopposite each other and need to be compressed together in order todisengage the grooves 261. The compression of one of the flanges 264 and266 alone will not disengage the collar 262 from the grooves 261. Inthis manner, collar 262 can not become accidentally disengaged duringthe rotation of the drill 250.

[0096] While it is believed that this mechanism is entirely novel, it isappreciated that various mechanisms to lockably adjust drills arewell-known to those skilled in the art. Such mechanisms include, but arenot limited to, the use of collets, threaded shafts with lock nuts, andflanges engaging grooves forced therein by either a cap pulled over theflanges or screwed down upon them.

[0097] Referring to FIGS. 13 and 14, in the preferred embodiment, theforward cutting edge 280 of drill 250 is a four cutting edge end millmodification of a large fluted drill design. The cutting portion 256 ofthe drill 250 resembles an end cutting mill which may contain anyworkable number of cutting surfaces, but preferably four or more, thatare relatively shallow such that the advancement of the drill 250 occursmore slowly. The cutting portion 256 of the drill 250 may be of adifferent diameter depending on the type of spinal implant that is beinginserted. If the spinal implant being inserted is threaded, the outsidediameter of the cutting portion 256 of the drill 250 would generallycorrespond to the minor diameter of the threaded implant. The innersleeve 242 has an inner diameter slightly greater than the minordiameter of a threaded implant and its outer diameter is slightlysmaller than the inside diameter of the extended outer sleeve 140 whichhas the same outer diameter as the major diameter (with threads) of thethreaded implant. If the implant is not threaded, the outside diameterof the drill 250 corresponds to the inside diameter of the extendedouter sleeve 140 such that a hole the maximum diameter of the extendedouter sleeve may be drilled.

[0098] The inner sleeve 242 serves many functions. First, it provides anintimate drill guide for drill 250 in the event a smaller diameter holeis to be drilled than that of the inside diameter of the extended outersleeve 140. Second, since the inner sleeve 242 guides the drill 250, itallows for the extended outer sleeve 140 to have an internal diameterlarge enough to admit a threaded implant, which is larger in diameterthan the outer diameter of the drill 240.

[0099] If a larger extended outer sleeve 140 were utilized absent theinner sleeve 242, then the drill 250 would be free to wander within theconfines of that greater space and would not reliably make parallel cutsremoving equal portions of bone from the adjacent vertebrae T₇ and T₈.Further, the bone removal not only needs to be equal, but must becorrectly oriented in three dimensions. That is, the path of the drill250 must be equally centered within the disc space, parallel theendplates, and perpendicular to the long axis of the spine dissectingthe disc space D.

[0100] A further purpose of the inner sleeve 242 is that it may beremoved simultaneously with the drill 250, thereby trapping the debris,both cartilaginous and bony, generated during the drilling procedure.The debris is guided rearward by the large flutes 251 of the lowercutting portion 256 and is collected around the central recessed portion254 and then contained and between the recessed portion 254 and theinner wall of the inner sleeve 242. Thus, by removing the drill 250 inconjunction with the inner sleeve 242, much of the debris generated bythe drilling procedure is safely removed from the drilling site.

[0101] Referring to FIG. 17, once the drill 250 and the inner sleeve 242are removed from the extended outer sleeve 140 a cylindrical hole 290remains across the disc space D and into the two adjacent vertebrae T₈and T₈. The cylindrical hole 290 is oriented across the transverse widthW of the vertebrae T₇ and T₈ in which an implant of appropriate diameteris to be implanted. The proper distraction and orientation of the twoadjacent vertebrae T₇ and T₈ is maintained by the extension member 148and the prongs 149 and 150 of the extended outer sleeve 140.

[0102] The cylindrical hole 290 may then be irrigated and vacuumedthrough the extended outer sleeve 140 to remove any remaining debrisfrom the drilling. If necessary, a thrombin soaked sponge may beinserted through the extended outer sleeve 140 and into the cylindricalhole 290 to coagulate any bleeding. The thrombin soaked sponge is thenremoved and the surgeon utilizing an endoscope then visually inspectsthe cylindrical hole 290 for any remaining discal material, and removesany such material requiring such removal with a surgical instrument suchas a curette or rongeur.

[0103] Referring to FIG. 18, with the extended outer sleeve 140 still inplace, the surgical site is now fully prepared to receive a spinalimplant I for fusion of the vertebrae T₇ and T₈. The spinal implant Imay be coated with, and/or made of, and/or loaded with substancesconsistent with bony fusion which may promote bone growth and/or fusionprior to being implanted. once the spinal implant I has been preparedfor implantation, a driver instrument, such as driver 300 may be used toeither insert or to remove spinal implant I. Driver 300 has at itsdistal end 302, a rectangular protrusion 304, which intimately engagesthe complimentary rectangular slot in the rear of implant I. Extendingfrom the rectangular protrusion 304 is threaded portion 306, whichextends as a rod through hollow shaft 308 and hollow barrel portion 310to knob 312 where it can be rotationally controlled. Threaded portion306 screws into a threaded aperture in the spinal implant I and bindingthem together such that driver 300 can be rotated via paired anddiametrically opposed extending arms 314 and 316 and in either directionwhile maintaining contact with the spinal implant I.

[0104] Affixed to the driver 300, the spinal implant I is thenintroduced through the extended outer sleeve 140 and if the spinalimplant I is threaded, screwed into the cylindrical hole 290 between thetwo vertebrae T₇ and T₈ until such time as the leading edge of theimplant cap 318 reaches the depth of the cylindrical hole 290 at whichtime its forward motion is impeded by the bone lying before it which hadnot been drilled out. This allows for a progressive feel to the surgeonas the spinal implant I is inserted into place. It is appreciated thatif the spinal implant I is not threaded, instead of being screwed intohole 290, it may be linearly advanced into hole 290 by pushing thedriver 300 toward the hole 290.

[0105] The terminal resistance to further seating provides significanttactile feedback to the surgeon. Visual monitoring of the depth ofinsertion of the spinal implant I is provided to the surgeon byobserving the progressive approximation of the forward surface 320, ofbarrel portion 310, as it approaches the rearward facing surface 172 ofextended outer sleeve 140 and/or by the use of an image intensifier. Asa final safety mechanism, when the full depth of insertion has beenachieved, forward surface 320 of instrument 350 will abut surface 172 ofthe extended outer sleeve 140, prohibiting any further installation ofthe implant. Once the spinal implant I has been fully installed, thedriver 300 is dissociated from the implant by turning knob 312 in acounterclockwise direction. The driver 300 is then withdrawn from theextended outer sleeve 140.

[0106] Referring to FIG. 19, the spinal implant I is shown fullyinstalled to the determined depth in the cylindrical hole 290 drilledacross the disc space D and into the adjacent vertebrae T₇ and T₈. Thespinal implant I shown comprises a hollow tubular member which in thepreferred embodiment is made of an ASTM surgically implantable material,preferably titanium. However, it is appreciated that other implants,cylindrical or partially cylindrical, or of a variety of shapes, andwith or without threads or surface roughenings may be used with theinstrumentation and method of the present invention.

[0107] Referring to FIG. 20 and 21, an extractor cap 340 for removingthe extended outer sleeve 140 is shown about to be coupled to theextended outer sleeve 140. The extractor cap 340 engages the proximalend 157 of the extended outer sleeve 140 by spring tabs 342 a and 342 bon either side of extractor cap 340 which snap-fit into openings 344 aand 344 b on either side of the extended outer sleeve 140 to lock inplace. The extractor cap 340 has a top 346 that is similar in structureto the proximal end of the distractor 100, having a recess portion 350and a crown portion 352.

[0108] Referring to FIG. 22, once the extractor cap 340 is coupled tothe extended outer sleeve 140, the distractor puller 200 is coupled tothe top 346 of extractor cap 340 to remove the extended outer sleeve 140from the disc space D and from the adjacent vertebrae T₇ and T₈ in thedirection of the arrow Z.

[0109] Referring to FIG. 23, once the extended outer sleeve 140 has beenremoved, the spinal implant I remains implanted within the cylindricalhole 290 drilled across the disc space D and the implant engages the twoadjacent vertebrae T₇ and T₈.

[0110] Referring to FIG. 24, the spinal implant I may be furtherstabilized with use of a spinal fixation device 400 such as the stapledisclosed in copending application Ser. No. 08/219,626 entitledAPPARATUS, INSTRUMENTATION AND METHOD FOR SPINAL FIXATION, which isincorporated herein by reference, The spinal fixation device 400 iscoupled to the spinal implant I with a locking screw 410 and engages thevertebrae T₇ and T₈ via prongs 420 and 422. The spinal fixation device400 functions to stabilize the spinal implant I and prevent any unwantedexcursion of the spinal implant I during the spinal fusion process. Itis appreciated that prior to removal of the extended outer sleeve 140, acentering post (not shown) may be inserted through the extended outersleeve 140 and attached to the threaded opening in the back of thespinal implant I. The extended outer sleeve 140 is then removed and thecentering post functions as guide to align the spinal fixation device400 as it is being driven into the vertebrae T₇ and T₈ as described indetail in the copending application referenced immediately above.

[0111] In the above description in regard to the thoracic spine, thesurgical procedure has been described as being performed through ahollow tube (extended outer sleeve 140) and with the aid of athorascope. It is appreciated that there may be circumstances where thesurgeon will elect to perform the surgical procedure through anincision, such as a thoracotomy, where direct visualization of thesurgical site is possible obviating the need for the thorascope butwithout diminishing the teaching of the method of the present invention.In such cases, a modification of the extended outer sleeve 140, such asthe extended outer sleeve 1100 shown in FIG. 35 and described in detailbelow, having a detachable distal end may be beneficially utilized bythe surgeon. In this manner, the surgeon has direct visualization of thesurgical site while the proper distraction and alignment of the adjacentvertebrae is maintained throughout the procedure by the distal end ofthe extended outer sleeve.

[0112] While the present invention has been described in associationwith the insertion of a threaded spinal implant, it is recognized thatother forms of implants may be used with the present method. Forexample, dowels, made from bone, coral or artificial materials, knurledor irregularly shaped cylinders or spheres, partial cylinders or anyother shaped implants that can be introduced through the extended outersleeve 140, which itself need not be cylindrical may be used.

[0113] When such implants are used, it is appreciated that the steps ofthe method of the present invention described above may be reduced. Forexample, once the extended outer sleeve 140 has been seated such thatthe extension portion 148 is inserted in the disc space D and the prongs149 and 150 engage the adjacent vertebrae, the step of inserting theinner sleeve 242 may be omitted and a drill having a diameterapproximating that of the inner diameter of the extended outer sleeve140 may be used to drill a hole the size of the inner diameter of theextended outer sleeve 140 across the disc space D and into the adjacentvertebrae. Once the drill has been removed, any remaining discalmaterial or debris may be removed by irrigating and vacuuming the hole,and an implant such as a bone dowel or an implant without threads, maybe linearly advanced through the extended outer sleeve 140 and implantedinto the hole. The extended outer sleeve 140 is then removed in the samemanner described above. Where the implant shape is generally notcircular, an appropriately shaped chisel may be used by itself or inconjunction with a drill to prepare an opening for the fusion implantthat is other than round.

[0114] It is further appreciated that it is also within the scope of thepresent invention to provide a method and instrumentation for theinsertion of a spinal implant into the disc space between two adjacentvertebrae, without the drilling away of significant bone from thevertebrae. Such implants may have a height corresponding to the heightof a disc space D and may be pushed into the disc space D whendistracted once the disc space D has been cleaned out. This type ofimplant would preferably have in part a rectangular cross section and anextended outer sleeve used for the insertion of such implants would havea corresponding cross section and shape. Further, it is appreciated thatthe extended outer sleeve and inner sleeve of the present invention mayhave any shape or size corresponding to the shape and size of theimplant to be inserted without departing from the scope of the presentinvention.

[0115] While the above description has been directed to the thoracicspine, the method and instrumentation of the present invention may alsobe utilized in the lumbar spine. In the preferred method, the surgeonmakes a small incision in the abdominal wall and gently dissects his wayretroperitoneal to reach the lateral aspect of the spine. As with thethorascopic method described above, the surgeon may use an endoscopewithin and/or outside of the extended outer sleeve to facilitate thesurgery, and thereby require an incision barely larger than the diameterof the extended outer sleeve which itself is not much larger than theimplant.

[0116] Referring to FIG. 25, an extended outer sleeve 1000 for use withthe lateral method in the lumbar spine is shown. The extended outersleeve 1000 is similar to the extended outer sleeve 140 described aboveand comprises a hollow tubular member 1002 having a distal end 1010which is contoured to hug the vertebrae, for example L₄ and L₅. Theextended outer sleeve 1000 has anterior and posterior extension members1020 and 1022, each having different heights, that are opposed 180degrees from each other. Also extending from the distal end 1010 may beprongs 1012 and 1014, similar to prongs 149 and 150 described above, forengaging the bone of the adjacent vertebrae L₄ and L₅. The extensionmembers 1020 and 1022 are tapered at their leading edges 1024 and 1026respectively, to facilitate insertion.

[0117] As shown in FIGS. 26-28, the extended outer sleeve 1000 isdesigned to be used in approaching the lumbar spine laterally fromeither side of the spinal column. The extended outer sleeve 1000 bymeans of its extended portions 1020 and 1022 is capable of correctingthose spinal deformities, such as scoliosis or any abnormality ofkyphosis or lordosis, occurring specifically from a deformity of thedisc. For example, in order to restore lordosis in the lumbar spine, theanterior extension member 1020 is placed anteriorly between the adjacentvertebrae L₄ and L₅ and the posterior extension member 1022, having alesser height than the extension member 1020, is placed posteriorly. Thegreater height of the extension member 1020 relative to the extensionmember 1022 maintains the anterior portions of the vertebrae L₄ and L₅spaced apart at a greater distance than the posterior portions of thevertebrae L₄ and L₅ producing an angular relationship between the bodiesas would exist with naturally occurring physiologic lordosis. Oncerestored, lordosis is maintained throughout the surgical procedure.

[0118] Scoliosis refers to an abnormal curving of the spine when viewedfrom straight ahead or behind. Since the extension members 1020 and 1022may be of a specific and constant height throughout their entirelengths, both sides of the disc space D are lifted to exactly the sameheight, thus eliminating any side to side angular deformity occurringthrough that disc space.

[0119] Referring specifically to FIG. 26, it can be appreciated that theposterior extension member 1022 effectively prevents any injury to thedural sac and neural elements, while the anterior extension member 1020in a similar fashion, protects the great blood vessels including theaorta, vena cava and the iliac arteries and veins. As the extended outersleeve 1000 of the present invention is quite stable once inserted, thepreferred embodiment is shown as having only two prongs 1012 and 1014,one each to engage each of the adjacent vertebrae L₄ and L₅. It is,however, understood that the extended outer sleeve 1000 may have more orless prongs or none at all. The distal end 1010 of the tubular member1002 is contoured adjacent the origin of the anterior and posteriorextended members 1020 and 1022 so as to assure an intimate fit betweenthe tubular member 1002 and the vertebrae L₄ and L₅ adjacent the discspace D to which it is opposed, and for the purpose of confining thesurgery to within the extended outer sleeve 1000 and excluding theadjacent soft tissues from potential injury. In the preferredembodiment, the distal end of the tubular member 1002 and the anteriorand posterior extended members 1020 and 1022 themselves have beenreinforced, that is are thicker than the adjacent tubular member 1002itself so as to provide for increased support within the lumbar spine.

[0120] Referring still to FIG. 26, the extended outer sleeve 1000engages the spine laterally, although the surgical approach in reachingthe spine may be from an anterior, lateral, or anterior-lateral incisionon the outside of the body, and is hereinafter referred to as the“Lateral Method”. The “Lateral Method” involves the insertion of adistractor, such as, but not limited to the distractor 100 describedabove into the lateral aspect of the spine, and generally from a side toside direction although said direction could be slightly fromanterolateral to slightly posterolateral (diagonalized from thetransverse axis) without departing from the teaching of the method ofthe present invention to distract the adjacent vertebrae, in thisexample, L₄ and L₅. Once the distractor 100 is in place, if fusion aloneis to be performed, then the extended outer sleeve 1000 having bothanterior and posterior extension members 1020 and 1022 is utilized. Theextended outer sleeve 1000 is placed over the distractor 100 such thatthe posterior extension member 1022 is positioned at the posterioraspect of the spine and the anterior extension member 1020 is positionedat the anterior aspect of the spine. Once the extended outer sleeve 1000is in place, the distractor 100 is removed. Alternatively, it isappreciated that the “Lateral Method” may be performed without the useof a distractor. Instead, the extended outer sleeve 1000 may be insertedfrom the lateral aspect of the spine directly since the extensionmembers 1020 and 1022 function to distract the adjacent vertebrae L₄ andL₅ to restore and maintain the normal angular relationship of thosevertebrae L₄ and L₅.

[0121] If the implant to be inserted has surface irregularities suchthat there is a major diameter (including the surface irregularities)and a minor diameter (excluding the surface irregularities), then aninner sleeve 1040 similar to the inner sleeve 242 described above, maybe inserted into the extended outer sleeve 1000. The inner sleeve 1040functions as a drill guide and spacer having a thickness whichcorresponds to the difference between the major and minor diameters ofsuch implant as described in detail above in reference to an innersleeve 1040. A drill 250, described above, is inserted into the innersleeve 1040 and is used to drill the vertebrae with the inner sleeve1040 providing a more intimate fit to the drill 250, than the largerbore of the extended outer sleeve 1000 could have alone and thus moreprecisely controlling the path of the drill 250. The inner sleeve 1040and the drill 250 may be removed from the extended outer sleeve 1000together thus trapping and removing much of the debris produced by theactual drilling. It is appreciated that in the alternative, a drill (notshown) may be used such that the distal bone engaging portion has anoutside diameter generally corresponding to the minor diameter of theimplant and more proximally, a shaft portion with a larger diametergenerally corresponding to the major diameter of the implant. An implantI may then be inserted according to the method described above. If theimplant to be inserted does not have a major and minor diameter, then noinner sleeve is required, and the drill 250 having a diametercorresponding with the diameter of such an implant may be inserteddirectly into extended outer sleeve to drill the vertebrae L₄ and L₅.

[0122] While not considered the preferred method under mostcircumstances it is nevertheless anticipated that one could drill thedescribed hole across the disc space and into each of the adjacentvertebrae from the lateral aspect of the spine and in at least apartially side to side direction through the extended outer sleeve andthen remove the extended outer sleeve and insert at least one spinalimplant also from the lateral aspect of the spine and in an at least apartially side to side direction and with or without the use of someform of spinal distractor. In which circumstance the use of an innersleeve is of less importance than that the size of the opening createdis sufficient such that it is possible to insert the implant. To thatend and independent of whether the extended outer sleeve is left inplace for implant insertion, and whether an inner sleeve is used duringdrilling it is anticipated and should be appreciated that the extendedouter sleeve and opening may be of a variety of shapes and that thecreation of spaces of varied shapes across a disc and within the spinemay be achieved by use of an instrument appropriate for the surgicalremoval of spinal material, such as a chisel or a router, and with orwithout the use of a drill, and/or an inner sleeve, and/or an extendedouter sleeve; and with the essential element being that the space withinthe spine is being created across a disc intermediate two adjacentvertebrae from the lateral aspect of said disc and at least in part in afrom side to side direction and that an implant is then inserted alsofrom the lateral aspect of said disc which implant occupies at least inpart said space, engages at least in part each of the vertebrae adjacentsaid disc space and comes to lie in an at least partially side to sidedirection across said disc space.

[0123] Referring to FIGS. 29 and 30, the implants I and J are showninserted across the disc spaces D between vertebrae L₃, L₄ and L₅,respectively. FIG. 30 is a top sectional view along lines 30-30 of FIG.29 showing the area of contact of the implant I and the vertebrae L₄. Itcan be seen from FIG. 30 that the implant I has a true lateralorientation with respect to the vertebra L₄, such that there is a greatarea of contact between the implant I and the vertebra L₄.

[0124] Referring to FIG. 30A, a top sectional view of a vertebra similarto FIG. 30 is shown illustrating the area of contact of the implant Iand the vertebrae L₄ when the implant I is inserted with the “LateralMethod” of the present invention from a slightly anterior position(anterolateral) along the Lateral aspect of the spine and in an at leastpartially side to side direction.

[0125] Referring to FIGS. 31 and 32, illustrating the prior art method,two implants 1050 and 1052 are inserted from the anterior or posterioraspect of the spine so that they are oriented in an anterior toposterior direction across the disc space D and vertebrae L₄ and L₅. Itcan be seen that implants 1050 and 1052 must have a much smallerdiameter than implant I to fit within the width of the spine andtherefore have very small areas of engagement to the vertebraethemselves as most of the diameter of the implants is used in justspanning across the height of the disc before contacting said vertebrae.FIG. 32 is a top sectional view along lines 32-32 of FIG. 31 showing thearea of contact of the two spinal implants 1050 and 1052 and thevertebra L₅.

[0126] Referring to FIG. 33, a top sectional view showing the area ofcontact of a cylindrical spinal implant 1090 having the same diameter asimplant I shown in FIG. 30, inserted from the anterior to posteriordirection across the vertebra L₅ is shown and seen to have by necessitya much shorter length.

[0127] Referring to FIGS. 30 and 32-33, it can then be appreciated thatan implant I inserted from the lateral aspect of the spine may have adiameter almost as great as the depth of the spine from front to back atthat location unlike two implants such as implants 1050 and 1052inserted side by side from front to back or the reverse where eachimplant can have a diameter no greater than one half the width of thespine at that level. It can further be appreciated that while the heightof the disc space itself hardly affects the area of contact of thesingle large implant I with the adjacent vertebrae, it substantiallyeffects the area of contact of the two implants 1050 and 1052 insertedin the front to back directions side by side. Further, as the lumbarvertebrae and discs are much wider from side to side then they are deepfrom front to back, it can be appreciated that when single implants ofthe same diameter are inserted across a given lumbar disc, the laterallyinserted implant I may be of a much greater length and thus have morearea of contact, for stability and fusion than implant 1090 insertedfrom anterior to posterior.

[0128] Referring to FIG. 34, a segment of the spinal column havingsingle implants 1095 and 1096 inserted from front to back at adjacentdisc levels between three vertebrae V₁₋₃ is shown. As it can be seen inFIG. 34, it is generally not possible to increase the diameter ofsingular implants inserted from front to back without risking severestructural and vascular damage to that area of the spine. Implants 1095and 1096 each have a diameter that is substantially greater than thediameter of implant 1090, such that implants 1095 and 1096 could intheory have a greater area of contact with the adjacent vertebrae thanimplant 1090. However, in application, as a result of the largerdiameter of the implants 1095 and 1096, a large portion of bone from theadjacent vertebrae would have to be removed to accommodate the largediameter of each of the implants 1095 and 1096 which would significantlyweaken the structural integrity of those vertebrae. This is especially aproblem when as shown in FIG. 34, implants 1095 and 1096 are inserted atadjacent disc levels such that the intermediate vertebrae V₂ would becut in half to form a “butterfly” pattern resulting in the complete lossof the structural integrity of vertebrae V₂.

[0129] Thus, the implant I of the present invention inserted laterallyprovides for greater surface area of contact, the largest volume offusion promoting material, and the greatest mechanical engagement andthus stability, and is therefore an improvement upon other methods ofimplant insertion in facilitating a successful fusion.

[0130] Referring to FIG. 35, an alternative embodiment of the extendedouter sleeve is shown and generally referred to by the numeral 1100. Asonly a single relatively small incision (approximately three inches orless) is required through the abdominal wall of the patient to performthe procedure for the fusion of two vertebrae adjacent a disc space inthe lumbar spine, it is anticipated that the surgeon may prefer toperform the method of the present invention under direct vision, withoutthe need for an endoscope. In such a circumstance, a convertibleextended outer sleeve 1100 may be used. The convertible extended outersleeve 1100 may be similar in structure to the extended outer sleeve1000, except that it comprises a hollow tubular member 1102 that isdisengageable from the distal end portion 1104 of the convertibleextended outer sleeve 1100. As shown in FIG. 35 the extended outersleeve 1100 has a detachable hollow tubular member 1102. The vertebraeengaging distal end portion 1104 may be as shown in FIG. 35 or may besimilar to the distal end shown previously in FIG. 7A, such that theconvertible extended outer sleeve 1100 may be useable throughout thespine.

[0131] The convertible extended outer sleeve 1100 is inserted in thedisc space D and the adjacent vertebrae L₄ and L₅ as described above forthe extended outer sleeve 1000. Once the extension member 1120 is seatedin the disc space D and the prongs 1112 and 1114 are engaged to thevertebrae L₄ and L₅, the hollow tubular member 1102 may be dissociatedfrom the distal end portion 1104 which remains engaged to the vertebraeL₄ and L₅. In this manner, if an incision is made to access the spinedirectly, the surgeon may access the disc space D through the distal endportion 1104 which is closer to the spine, without having to passthrough the entire length of the convertible extended outer sleeve 1100.With the distal end portion 1104 in place, the vertebrae remaindistracted and aligned, and since the hollow tubular member 1102 hasbeen removed, it is then possible for the surgeon to work in and aroundthe spine under direct vision. The shortened distal end portion 1104 ofthe convertible extended outer sleeve 1100 left protruding from theadjacent vertebrae may be selected to be of a length such that it stillserves to offer some protection to the large blood vessels which aresafely positioned outside of the remaining working channel.Alternatively it can be of any length so as to fulfill the surgeon'spurposes. The hollow tubular member 1102 may be re-engaged to the distalend portion 1104 for inserting an implant I in the manner describedabove.

[0132] In the specific embodiment of the convertible extended outersleeve 1100, the distal end portion 1104 has a single extension member1120 and two prongs 1112 and 1114 positioned approximately 120 degreesfrom the extension member 1120 for engaging the two adjacent vertebraeL₄ and L₅, for the purpose of allowing the surgeon direct access to thespinal canal. Thus, if a discectomy is to be performed, an extendedouter sleeve having a single anterior intradiscal extended member 1120,but without a posterior extended member, and with two vertebrae engagingprongs 1112 and 1114 may be used.

[0133] It is appreciated that for surgery on the thoracic spine, whilethe method described above wherein the entire procedure is performedthrough the extended outer sleeve 140 is preferred, it is also possibleto utilize the convertible extended outer sleeve 1100 when a fullthoracotomy is made to access the thoracic spine without having to workthrough the entire length of the extended outer sleeve. In this mannerthe surgeon may directly visualize and access the surgical site.

[0134] Further, combining the features of the absence of any posteriorintradiscal extended member with the convertible extended outer sleeve1100 permits easy and direct access to the spinal canal for removal ofany diseased discal material.

[0135] While the present invention has been described in detail withregards to the preferred embodiments, it is appreciated that othervariations of the present invention may be devised which do not departfrom the inventive concept of the present invention.

What is claimed is:
 1. A method of inserting an intraspinal implant fromthe lateral aspect of the human spine, comprising the steps of: (a)making a penetration from the lateral aspect of a spinal discintermediate two adjacent vertebrae; (b) removing at least a portion ofsaid spinal disc; and (c) inserting through said penetration at leastone implant between said adjacent vertebrae.
 2. The method of claim 1including the step of placing an extended outer sleeve at the lateralaspect of the spine.
 3. The method of claim 2 in which said extendedouter sleeve includes engagement means for engaging the spine.
 4. Themethod of claim 3 in which said engagement means comprises penetratingmeans for penetrating at least one of said adjacent vertebrae.
 5. Themethod of claim 3 in which said engaging means comprises at least onedistal extension.
 6. The method of claim 3 in which said extended outersleeve comprises at least one extended member that is driven into saidspinal disc from the lateral aspect of the spine in at least a partiallyside to side direction across said spinal disc.
 7. The method of claim 3in which said extended outer sleeve comprises distraction means forspacing apart said adjacent vertebrae.
 8. The method of claim 3 in whichsaid extended outer sleeve includes means for corrective realignment ofsaid vertebrae adjacent said disc space.
 9. The method of claim 3 inwhich the extended outer sleeve is dissociateable into a proximalportion being furthest from the spine, and a distal portion beingadjacent and oriented lateral to the spine; said extended outer sleevebeing dissociated such that said proximal portion is removed and saiddistal portion is left in place for at least a portion of said method.10. The method of claim 3 in which a portion of said extended outersleeve protrudes outside the body of a patient for at least a portion ofsaid method.
 11. The method of claim 3 in which at least a part of saidextended outer sleeve is tubular.
 12. The method of claim 1 includingthe step of driving toward the lateral aspect of the spine an extendedouter sleeve having a distraction means for distracting a disc spacebetween two adjacent vertebrae and inserting the distraction means intosaid disc space.
 13. The method of claim 3 including the step ofinserting a drill into said extended outer sleeve and drilling a holeacross a disc space between two adjacent vertebrae and into the twoadjacent vertebrae.
 14. The method of claim 3 in which hand heldinstruments are inserted through said extended outer sleeve to remove aportion of spinal disc material adjacent the spinal canal.
 15. Themethod of claim 14 in which an endoscopic viewing device is passed downthrough said extended outer sleeve to observe said removal of a portionof spinal disc material.
 16. The method of claim 3 including the step ofinserting an implant through at least a portion of said extended outersleeve and between the adjacent vertebrae.
 17. The method of claim 1 inwhich said implant is oriented at least partially in a side to sidedirection across the adjacent vertebrae and occupies at least in part aportion of a space created by the removal of said portion of said spinaldisc.
 18. The method of claim 1 in which said implant engages at leastin part a portion of each of said adjacent vertebrae.
 19. The method ofclaim 1 in which said implant is inserted in at least a partial side toside direction across said adjacent vertebrae.
 20. The method of claim 1in which at least a portion of the step of removing said spinal disc isperformed with a drill.
 21. The method of claim 1 including the step ofremoving at least a portion of bone from at least one of said adjacentvertebrae.
 22. The method of claim 21 in which at least a part of saidstep of removing a portion of bone is performed by drilling.
 23. Themethod of claim 1 in which a drill is used to remove at least a portionof said spinal disc and at least a portion of bone from each of theadjacent vertebrae.
 24. The method of claim 3 including the steps ofinserting a drill through at least a portion of said extended outersleeve from the lateral aspect of the spine, drilling at least a portionof said disc and at least a portion of bone from each of the adjacentvertebrae, and removing said drill.
 25. The method of claim 24 includingthe step of removing any debris left in a space formed by the drillingfollowing the removal of the drill.
 26. The method of claim i in which achisel is used to remove a portion of at least one of said adjacentvertebrae.
 27. The method of claim 24 in which said drill passes througha hollow inner sleeve fitting at least in part around said drill, saidinner sleeve having at least a portion thereof fitting within saidextended outer sleeve.
 28. The method of claim 3 including the step ofinserting a hollow inner sleeve member into said extended outer sleeve.29. The method of claim 28 in which said hollow inner sleeve member isremoved from said extended outer sleeve prior to the step of insertingsaid implant.
 30. The method of claim 28 including the steps of passinga drill through said hollow inner sleeve member, penetrating said spinaldisc from the lateral aspect of the spine and penetrating across atleast a part of said spinal disc in at least a partial side to sidedirection across said adjacent vertebrae.
 31. The method of claim 1including the step of engaging an alignment means to the spine from thelateral aspect of the spine.
 32. The method of claim 31 in which saidalignment means is a rod inserted from the lateral aspect of the spineinto said spinal disc.
 33. The method of claim 31 including the step ofplacing an extended outer sleeve over said alignment means.
 34. Themethod of claim 31 in which said alignment means is at least in parthollow.
 35. The method of claim 34 including the steps of inserting intothe lateral aspect of said spinal disc a guide pin having at least aportion extending laterally from said spinal disc, and placing saidalignment means over said guide pin.
 36. The method of claim 31 in whichsaid alignment means is an intervertebral distractor that spaces apartthe adjacent vertebrae.
 37. The method of claim 36 in which at least apart of said distractor is hollow.
 38. The method of claim 31 in whichsaid alignment means has a distal end portion for insertion into saidspinal disc, said distal end portion capable of distracting a disc spacebetween two adjacent vertebrae and urging said adjacent vertebrae apart.39. The method of claim 1 including the step of distracting apart saidadjacent vertebrae.
 40. The method of claim 2 including the steps ofinserting a guide pin into a disc space between said adjacent vertebraeprior to the step of placing said extended outer sleeve; placing overthe guide pin an alignment rod having a penetrating portion and apassageway for receiving the guide pin; and inserting said penetratingportion into said disc space.
 41. The method of claim 1 including thestep of inserting distraction means into a disc space between saidadjacent vertebrae.
 42. The method of claim 41 in which said distractionmeans comprises a first extension member for insertion in the discspace.
 43. The method of claim 42 in which said distraction meansincludes a second extension member for insertion in the disc space. 44.The method of claim 28 including the step of inserting into the lateralaspect of a spinal disc a distractor having a penetrating portion priorto the step of inserting said extended outer sleeve.
 45. The method ofclaim 1 including the step of inserting a guide pin toward the lateralaspect of the spine into the lateral aspect of said spinal disc in whichat least a portion of said guide pin remains protruding from said spinaldisc.
 46. The method of claim 45 including the steps of placing oversaid guide pin a hollow distractor having a penetrating portion and apassageway for receiving the guide pin and inserting said penetratingportion into a disc space between said two adjacent vertebrae.
 47. Themethod of claim 2 including the steps of making at least one incisionalong the lateral chest wall of a patient and driving said extendedouter sleeve through said incision to the lateral aspect of the thoracicspine.
 48. The method of claim 1 including the step of making at leastone incision into the lateral aspect of the body of a patient for thepurpose of accessing the lateral aspect of the spine.
 49. The method ofclaim 1 in which said method is performed in the lumbar spine andincludes the step of first approaching the lateral aspect of at leastone spinal disc and at least a portion of the two vertebrae adjacentsaid disc by means of a retroperitoneal surgical dissection.
 50. Themethod of claim 1 in which said method is performed from the lateralaspect of the spine and directed at least partially from side to sideacross said adjacent vertebrae.
 51. The method of claim 3 in which saidextended outer sleeve has portions penetrating into the spinal column,said portions extending from the distal end of said extended outersleeve to penetrate said spinal column and are oriented in at least apartial side to side direction across said adjacent vertebrae.
 52. Themethod of claim 1 including the step of tapping said adjacent vertebrae.53. The method of claim 3 including the step of tapping said adjacentvertebrae.
 54. The method of claim 53 in which said tap passes throughat least a portion of said extended outer sleeve.
 55. The method ofclaim 1 in which an endoscope is used during at least a portion of themethod.
 56. The method of claim of 1 in which a radiographic imagingdevice is utilized during at least a portion of the method.
 57. Themethod of claim 1 including the step of coupling a spinal fixationdevice to the spinal implant and engaging the spinal fixation device tothe adjacent vertebrae.
 58. A method of inserting an intraspinal implantfrom the lateral aspect of the spine, comprising the steps of: (a)making a penetration from the lateral aspect of a spinal discintermediate two adjacent vertebrae; (b) firmly engaging the lateralaspect of the spine with a hollow tubular member; (c) removing at leasta portion of said spinal disc through said hollow tubular member; and(d) inserting through said hollow tubular member at least one implantbetween said adjacent vertebrae.
 59. A method of insertion anintraspinal implant from the lateral aspect of the spine, comprising thesteps of: driving toward the lateral aspect of a spinal discintermediate two adjacent vertebrae an extended outer sleeve havingengaging means for engaging the spine along its lateral aspect; removingthrough at least a portion of said extended outer sleeve at least aportion of said spinal disc; and inserting into the lateral aspect ofthe spine at least one implant, said implant occupying at least in partthe space created by the removal of said portion of spinal disc.
 60. Amethod for inserting a spinal implant across two adjacent vertebrae inthe spine from the lateral aspect of the spine using a distracting meansto space apart said adjacent vertebrae; approach, comprising the stepsof: inserting from the lateral aspect of the spine an extended outersleeve having engagement means for engaging the spine; engaging saidextended outer sleeve to the spine: removing said distractor means;removing at least a portion of a spinal disc intermediate said adjacentvertebrae; inserting an implant through at least a portion of saidextended outer sleeve into the disc space; and removing the extendedouter sleeve.
 61. The method of claim 60 including the step of insertingan alignment means having a penetrating portion into the disc space; 62.The method of claim 60 in which said engagement means comprises a seconddistractor means for distracting the disc space between two adjacentvertebrae.
 63. The method of claim 60 including the step of inserting aninner sleeve into the extended outer sleeve.
 64. The method of claim 60including the step of inserting a drill into the inner sleeve.
 65. Themethod of claim 60 in which the step of removing said spinal discincludes drilling a hole across the disc space and into the two adjacentvertebrae.
 66. The method of claim 60 in which said distractor meanscomprises an alignment means.
 67. A distractor instrument fordistracting the disc space between two adjacent vertebrae in the spinefrom the lateral aspect of the spine, comprising a penetrating portionfor insertion in the disc space between two adjacent vertebrae, saidpenetrating portion having a length that is less than the transversewidth of the vertebrae and greater than the anterior to posteriordimension of the vertebrae.
 68. The distractor instrument of claim 67 inwhich said distractor instrument has a longitudinal passageway forreceiving an alignment means.
 69. The distractor instrument of claim 67in which said distractor instrument comprises a barrel portionterminating in said penetrating portion, said barrel portion having alarger diameter than said penetrating portion.
 70. The distractorinstrument of claim 69 in which said distractor instrument includes ashoulder at the junction of said penetrating portion and said barrelmember for preventing said barrel member from entering the disc space.71. The distractor instrument of claim 67 in which said distractorinstrument includes means for engaging an extraction instrument forremoving said distractor instrument from within the disc space.
 72. Asurgical instrument comprising a hollow tubular member and an engagementmeans for engaging the lateral aspect of the spine.
 73. The surgicalinstrument of claim 72 in which said engagement means comprises at leastone extension member for insertion into a spinal disc intermediate twoadjacent vertebrae along the lateral aspect of the spine, said extensionmember being oriented at least in part along the transverse width of thespine when said surgical instrument is engaged to the lateral aspect ofthe spine.
 74. The surgical instrument of claim 73 in which saidextension member extends at least in part transversely across the spinaldisc within the anterior aspect of the spinal disc when said surgicalinstrument is engaged to the lateral aspect of the spine.
 75. Thesurgical instrument of claim 74 in which said engagement means includesa second extension member extending at least in part transverselythrough the posterior aspect of said spinal disc when said surgicalinstrument is engaged to the lateral aspect of the spine.
 76. Thesurgical instrument of claim 72 in which said engagement means comprisesat least one penetrating member for penetrating at least one of twovertebrae adjacent a spinal disc.
 77. The surgical instrument of claim72 in which said instrument comprises at least two extension members.78. The surgical instrument of claim 76 including a second penetratingmember for penetrating the second of said two adjacent vertebraeadjacent a spinal disc.
 79. The surgical instrument of claim 72 in whichsaid engagement means for engaging the lateral aspect of the spine ispositioned at the distal end of said hollow tubular member, saidengagement means being capable of centering said hollow tubular memberwith respect to the height of a spinal disc and the vertebrae adjacentsaid spinal disc from the lateral aspect of the spine.
 80. The surgicalinstrument of claim 72 in which said hollow tubular member has asufficient length to protrude from the lateral aspect of the human bodywhen said surgical instrument is engaged to the lateral aspect of thespine.
 81. The surgical instrument of claim 72 in which said hollowtubular member has a length which can be changed while said surgicalinstrument in engaged to the lateral aspect of the spine.
 82. Anextended outer sleeve for use in inserting a spinal implant into a holeformed across a disc space and into two adjacent vertebrae from thelateral aspect of the spine, comprising a hollow tubular member havingat one end a distraction means for distracting and aligning the twoadjacent vertebrae.
 83. The extended outer sleeve of claim 82 in whichsaid distraction means comprises a first extension member for insertioninto the disc space.
 84. The extended outer sleeve of claim 83 in whichsaid distraction means includes a second extension member for insertionin the disc space.
 85. The extended outer sleeve of claim 82 in whichsaid first extension member is substantially in line with the exteriorsurface of said extended outer sleeve.
 86. The extended outer sleeve ofclaim 82 in which said first extension member has a height that issubstantially equal to the normal height of the disc space between twoadjacent vertebrae.
 87. The extended outer sleeve of claim 82 in whichsaid first extension member comprises a tapered leading edge tofacilitate insertion.
 88. The extended outer sleeve of claim 82 in whichsaid extended outer sleeve includes engagement means for engaging atleast one of the two adjacent vertebrae.
 89. The extended outer sleeveof claim 88 in which said engagement means comprises at least onepenetrating member for penetrating the bone of at least one of the twoadjacent vertebrae.
 90. A depth limiting device for a surgicalinstrument having a shaft and a grooved portion on said shaft, saidsurgical instrument being operated through a guide means having apassage way for receiving said shaft, comprising: an adjustable collarfor limiting the depth of said surgical instrument engaging said shaft,said collar having a diameter larger than the diameter of said shaft andlarger than said passageway; and a pair of diametrically opposed flangemembers pivotably mounted to said collar capable of engaging saidgrooved area, said flanged members being spring biased to engage saidgrooved portion when biased, and disengage said grooved portion whenunbiased.
 91. The method of claim 1 in which said implant occupies morethan one half of the depth of the spinal disc, said depth measured fromthe anterior aspect to the posterior aspect of said spinal disc.
 92. Themethod of claim 1 in which at least two implants are inserted.
 93. Themethod of claim 92 in which said at least two implants have a combinedwidth that is greater than one half the depth of said spinal disc, saiddepth being measured from the anterior aspect to the posterior aspect ofsaid spinal disc.
 94. The method of claim 19 in which said implant has awidth of at least 20 millimeters, said width being measured across thespinal disc from the anterior aspect to the posterior aspect of thespinal disc.